From nobody Mon Feb 9 11:28:11 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82C652882D1 for ; Wed, 14 May 2025 18:42:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747248125; cv=none; b=Xfn9qhIwvjzdPIb2XMA/z4s2L/aaPzL88SeIf4F1YkXmeZPYelLMfyZlGgTSV58ywropYzXJIFZMhMqun3Yv2vRUDYacyh8s7CcdIDNgm8y2f1EPeqn92bX8589LoC3dUIyWwuik4Zy4zIwdMekLELosLACl1R6WsnghoPWBhqo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747248125; c=relaxed/simple; bh=8WPS6fJFn9ZOxrssZfprQKVrhRW5a0xtdjp+RK/angE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=nOT4qTtSzfGchsCMlCEWL8IaoxsPc9R2kClfAvxrCS96Sj9dxzwm2dC1X2P9WkEQnaybQxNa5aN53EiEhGYqJk3NnaGPbER5dnOxbj/jKrO6N5kq7ljV7dV9TNoHmknZEbHVhqOYp47ImUOiat9AeeuRkTX7Y0geaoH3la0b08w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--dionnaglaze.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=p8NkvsKP; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--dionnaglaze.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="p8NkvsKP" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-b1ffc678adfso30401a12.0 for ; Wed, 14 May 2025 11:42:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1747248123; x=1747852923; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=CYJuHf6JfZCBn/xacOL2tI46jqMW4+1r9XjhA6jdQBY=; b=p8NkvsKPnNZ+zrvsTHEQjWzLb7E6Mb53DL0RSpRW1F0PrZPxzKFPKssadzM+phgSff I/tpjw3zfzsIcXCB7DYeWvJ0y4rlPMZC3a+3v+0S5idn4r+YTo/w5w9rcCEvFlanBN/m GT/hyb7gpk/WM5Bc41F/XzqVMVLqtGijFzeDWokwbhMsqBEc9CepwWJkUk2zztEKMYn5 B55/G0ClyEvabZaNtJCXr9u2jDp9Xlnb9al53MaiJtSQx/kijKgz7B/TSacbPV5++FAY MF6beYoWQg2FNYQx6QVN39v6MztgFbjpEXX8PDz6iMmXTT7aoBQpKT5uaZqRau87Wm7F yv0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747248123; x=1747852923; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=CYJuHf6JfZCBn/xacOL2tI46jqMW4+1r9XjhA6jdQBY=; b=uw+hit6gvFdo52bkSuebGF6ujtfKFFUHHdvfpmQyjmd5tHrGdeVcpY7v/Fut94qcRO 6dM5tRqK3MfMZCzwGBjZnnSbl7wj20jskZUuPejnJ/6Qs3NrQ+cAfuLNHw2o7ufmd0ND qFksKj8a5e3GR3LA4kNi0P41AdS4gqnhbYU94jxQ5FSLKWW8AdqxS1GtDRjsyvCf/GY0 wkUUzS4yRAIh+QBXhwX5u6UlF2lI30ibXT/1Z9nGMo/ts8Hk/hLwTaxbySDpZDNIpQTi oy7Za0CRAE/ZFjvu/4JOdpLdeELbJ+DIutSfN9j8qPa1yFS3CwzLe0L/dnhTh+5SCDNy Zdsg== X-Gm-Message-State: AOJu0YylS6hk+4Jdc/pzMrXmj7d2v7putCKx6ODDL4aDlUsnoB3m5LE0 9xm3A8SApQfSBTWMu+HUqhQ633PSsc9E22HOMKqOX1S26iMYmOy/zX93wdVSbI1Na7te3JO2NsK l4KorZ+vMm29tFjJBLmsyPg== X-Google-Smtp-Source: AGHT+IHaW0tGNG2An47wn7ypYPKbD5kAKXhci3mLdyKHvLgmgeV/RB/EAKA0ZnHx69e5p2D6/yHVAiXZ18yI4rGUsg== X-Received: from pfks12.prod.google.com ([2002:a05:6a00:194c:b0:740:6f6:7346]) (user=dionnaglaze job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:6d88:b0:1f5:5ca4:2744 with SMTP id adf61e73a8af0-215ff0d4647mr5637627637.17.1747248122860; Wed, 14 May 2025 11:42:02 -0700 (PDT) Date: Wed, 14 May 2025 18:41:36 +0000 In-Reply-To: <20250514184136.238446-1-dionnaglaze@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250514184136.238446-1-dionnaglaze@google.com> X-Mailer: git-send-email 2.49.0.1045.g170613ef41-goog Message-ID: <20250514184136.238446-4-dionnaglaze@google.com> Subject: [PATCH v4 2/2] The ccp driver can be overloaded even with guest request rate limits. The return value of -EBUSY means that there is no firmware error to report back to user space, so the guest VM would see this as exitinfo2 = 0. The false success can trick the guest to update its message sequence number when it shouldn't have. From: Dionna Glaze To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Dionna Glaze , Thomas Lendacky , Paolo Bonzini , Joerg Roedel , Peter Gonda , Borislav Petkov , Sean Christopherson Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Instead, when ccp returns -EBUSY, that is reported to userspace as the throttling return value. Cc: Thomas Lendacky Cc: Paolo Bonzini Cc: Joerg Roedel Cc: Peter Gonda Cc: Borislav Petkov Cc: Sean Christopherson Signed-off-by: Dionna Glaze --- arch/x86/kvm/svm/sev.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index ddbfdce9dc18..5901a7f59f88 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -4065,6 +4065,11 @@ static int snp_handle_guest_req(struct vcpu_svm *svm= , gpa_t req_gpa, gpa_t resp_ * the PSP is dead and commands are timing out. */ ret =3D sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &fw_err); + if (ret =3D=3D -EBUSY) { + svm_vmgexit_no_action(svm, SNP_GUEST_ERR(SNP_GUEST_VMM_ERR_BUSY, fw_err)= ); + ret =3D 1; + goto out_unlock; + } if (ret && !fw_err) goto out_unlock; =20 --=20 2.49.0.1045.g170613ef41-goog